Add possibility to set individual logo for CMS branding

[ulliholtgrave]

Motivation

Provide the possibility to change the logo to a specific one to provide the opportunity to brand the cms to your organization.

Proposed Solution

Add a setting that defines the path to the logo and use it in all relevant files (e.g. templates and tailwind with integreat_logo as default value).

[svenseeberg]

@ulliholtgrave I just realized that we do not have a custom logo for Malte in the current Malte CMS. Let's skip this issue for now, as this is more work than expected. We probably want to change this issue into "Support custom CSS" or similar.

[ulliholtgrave]

@svenseeberg But aren't we using the default Malteser logo in the current cms.

[svenseeberg]

No, we're not :)